/usr/lib/mon/mon.d/ is in mon-contrib 1.0+dfsg-2.
This file is owned by root:root, with mode 0o755.
..
/usr/lib/mon/mon.d/bgp.monitor
/usr/lib/mon/mon.d/cisco-env.monitor
/usr/lib/mon/mon.d/citrix.monitor
/usr/lib/mon/mon.d/dhcp.monitor
/usr/lib/mon/mon.d/dir_file_age.monitor
/usr/lib/mon/mon.d/flexlm.monitor
/usr/lib/mon/mon.d/ftps.monitor
/usr/lib/mon/mon.d/http_integrity.monitor
/usr/lib/mon/mon.d/https.monitor
/usr/lib/mon/mon.d/icecast.monitor
/usr/lib/mon/mon.d/imap-ptp.monitor
/usr/lib/mon/mon.d/imap-ssl.monitor
/usr/lib/mon/mon.d/imap-starttls.monitor
/usr/lib/mon/mon.d/imsp.monitor
/usr/lib/mon/mon.d/informix.monitor
/usr/lib/mon/mon.d/informixdbspace.monitor
/usr/lib/mon/mon.d/ipsec.monitor
/usr/lib/mon/mon.d/ipvs.monitor
/usr/lib/mon/mon.d/krb5.monitor
/usr/lib/mon/mon.d/lmtp.monitor
/usr/lib/mon/mon.d/mailloop.monitor
/usr/lib/mon/mon.d/mupdate.monitor
/usr/lib/mon/mon.d/netsnmp-exec.monitor
/usr/lib/mon/mon.d/netsnmp-freespace.monitor
/usr/lib/mon/mon.d/netsnmp-proc.monitor
/usr/lib/mon/mon.d/netwarefree.monitor
/usr/lib/mon/mon.d/ospf.monitor
/usr/lib/mon/mon.d/postgresql.monitor
/usr/lib/mon/mon.d/printmib.monitor
/usr/lib/mon/mon.d/process-full-command-line.monitor
/usr/lib/mon/mon.d/ps.monitor
/usr/lib/mon/mon.d/pubcookielogin.monitor
/usr/lib/mon/mon.d/rbl.monitor
/usr/lib/mon/mon.d/remote.monitor
/usr/lib/mon/mon.d/rptr.monitor
/usr/lib/mon/mon.d/samba.monitor
/usr/lib/mon/mon.d/smblist.monitor
/usr/lib/mon/mon.d/smtp-ssl.monitor
/usr/lib/mon/mon.d/smtp_rt.monitor
/usr/lib/mon/mon.d/snmp_interface.monitor
/usr/lib/mon/mon.d/softraid.monitor
/usr/lib/mon/mon.d/sqlconn.monitor
/usr/lib/mon/mon.d/ssh.monitor
/usr/lib/mon/mon.d/startremote.monitor
/usr/lib/mon/mon.d/storage.monitor
/usr/lib/mon/mon.d/sybase.monitor
/usr/lib/mon/mon.d/tcpch.monitor
/usr/lib/mon/mon.d/tftp.monitor
/usr/lib/mon/mon.d/udp.monitor
/usr/lib/mon/mon.d/umn_mon.monitor
/usr/lib/mon/mon.d/webapp.monitor